Please Refer : http://www.c-sharpcorner.com/UploadFile/dhananjaycoder/keep-your-code-dry/

DRY just means "Don't Repeat Yourself". Make sure that when you write code, you only write it one time. If you find yourself writing similar functionality in all of your Controller classes, make a base controller class that has the functionality and then inherit from it, or move the functionality into another class and call it from there instead of repeating it in all the controllers